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Carb adjustment

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IowaTom

Carb adjustment

Guys - After blowing compressed air thru the gas line and installing a new tank & sender, she fired right up!

Thank you all for the suggestions!

Now I've got a question about the carb that came with my truck. The neighbor who sold her to me said he replaced the old one with this and I'd like to make an attempt at finding a good mix. Years ago I remember using a vacuum gauge to adjust the air-fuel screw for about 20". Would that still be applicable with this carb?

'85 F150 XLT 4X4 with 300 c.i. six & NP435 four speed.
'63 Studebaker Avanti - 350/TH350
'59 Rambler Super - OHV 6 with 3-speed OD
'58 Studebaker Scotsman sedan - 289 with 3-speed OD

Gary Lewis

Re: Carb adjustment

Administrator

Glad you got it going!

And yes, you should be able to get 20" of vacuum at idle. But in reality you just go for max vacuum, dropping the idle speed back to where you want it as it increases with the increased vacuum. And then give it 1/8 to 1/4 turn more open on the screw to make it slightly richer.

Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

IowaTom

Re: Carb adjustment

Thanks, my friend!

'85 F150 XLT 4X4 with 300 c.i. six & NP435 four speed.
'63 Studebaker Avanti - 350/TH350
'59 Rambler Super - OHV 6 with 3-speed OD
'58 Studebaker Scotsman sedan - 289 with 3-speed OD

1986F150Six

Re: Carb adjustment

Administrator

On my 1986 with 4.9L [computer control removed], I found that with 20" vacuum at idle, pinging would occur when under a load. At ~18.5", all was good.

IowaTom

Re: Carb adjustment

That appears to be the sweet spot for my engine, too.

As for the old tank, cleaning it myself made no difference in the amount of crud. SO glad I bought a new one! If you're considering trying to DIY, fahgetaboutit!

'85 F150 XLT 4X4 with 300 c.i. six & NP435 four speed.
'63 Studebaker Avanti - 350/TH350
'59 Rambler Super - OHV 6 with 3-speed OD
'58 Studebaker Scotsman sedan - 289 with 3-speed OD

ArdWrknTrk

Re: Carb adjustment

Administrator

I replaced my mid-ship tank recently because the straps or frame had fretted a pinhole leak that would make it wet if I filled up.
I could smell gas but never found any drips.
For $150 delivered with new straps it wasn't worth my time to even think about it.
I'm glad too. 🙂 The new one appears powder coated or something. Much better than the last one I installed in the rear.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

1986F150Six

Re: Carb adjustment

Administrator

Pardon the highjack, but this thread reminded me of something:

For whatever it is worth, and the truck show is still far away, I have an original 16 gallon side tank and sending unit from a 1985 F150 truck which had 61K miles. If anyone is interested in originality, I could deliver to Skiatook. The engine was a 4.9L, so the sending unit does not have a fuel pump.